Physical activity (PA) benefits children's cognition, in particular executive functions (EF). Children with Attention Deficit Hyperactivity Disorder (ADHD), Reading Difficulties (RD) and co-occurring ADHD/RD have low levels of PA and difficulties with EF. This study evaluated a PA programme to determine recruitment, attrition, feasibility (e.g. in-school or after-school hours), intensity of PA during the programme and effect sizes. Outcomes evaluated were EF, academic attainment and social and emotional behaviour. Sixty-nine children (35 males) aged 7-13 years participated in a delayed control design. The sample comprised 15 children with RD, 15 with high levels of ADHD symptoms, 15 with co-occurring RD and ADHD symptoms and 24 typically developing children. Thirty-one of the participants took part in a 12 week PA intervention designed to enhance cognition and 38 acted as a control group. The control group subsequently received the intervention and data was combined for analysis. The study was successful in recruiting participants for the intervention; more success was observed for in-school than after-school hours. Participants spent 46% (SD = 14) of the intervention in Moderate-to-Vigorous intensity PA (MVPA). A significant effect of time-point (pre- vs. post-intervention) was found for inhibition and visuospatial working memory ([eta][superscript 2] = 0.11 and 0.18 respectively). There was no interaction with symptomatology though; all groups had higher scores on EF tasks after the intervention. It is possible to recruit and retain participants with ADHD symptoms and reading difficulties to a school-based PA programme and adherence to measurements was good. Taking part in the programme may improve inhibition and visuospatial working memory and reduce symptomatology suggesting this is a potential source of remediation which should be explored.